Variable condenser



Feb. 22, 1927. 1,618,399

-R. M. WISE ET AL VARIABLE CONDENSER Filed July 26. 1924 2 Sheets-Sheet1 IH v FIG-'2.

I M B T BY rmmr Arron/mys- Feb. 22 1927.

R. M. WISE ET AL .VARIABLE CONDENSER Filed July 26. 1924' 2 Sheets-Sheet2 length range is increased.

Patented Feb. 22, 1927.

IT-En stares .PAT

FiNT OFFICE.

mass M. WISE, or OAKLAND, AND ERNEST e. DANIELSON, or SAN FRANCISCO,CALI? EORNIVAFASSIGNORS TO E. '1. CUNNINGHAM, or SAN FRANCISCO,CALIFORNIA.

VARIABLE Application filed July as,

as isspecially adapted for the control of.

high frequency 'circuits,as for instance in radio communication systems.7 Variable condensers having interleaving 'plateshave' been in use for aconsiderable period'for this purpose, but as constructed they presentcertain disad anta-geous effects that our invention is ai'med toovercome.

These condensers are used in a large mafjority of instances to tune highfrequency circuits so as to make them resonant to a very narrowrange'o'f frequencies, as is well understood. 'When so'used, it ishighly important to perform adjust-mentshaving comparatively fineeffects on the circuit. With the'iusual type of condenser having rotaryplates interleaving stationary plates, the variation incapacity cannotreadily be made such as to provide uniform wave length variation'atwhich th'ecircuit is resonant, for uniform variations in the setting;furthermore it is diflicult to secure fine adjust- I ment, the rotaryplates having only about a 180 movement plates;

It is one of the objects of our invention to overcome thesedisadvantages in a large measure, and to make-it possible to secureaccurate ad ustment as well as uniform wave relative to the stationarylength variation.

Another serious defect in condensers of the prior art resides in thefact that the insulation between the electrodes of the condenser is'so'distributed as to-fall within relatively intense electricfi-eld's,whereby a large dielectric'loss results. This in turn not onlyreduces the sharpness of tuning, but also the -.inten sity' of'thesignal. It is anotherobject of our invention to provide a low losscondenser b removing all insulation out of the intense eld, I

It is also another object ofour invention to provid'ea variablecondenser havinga low minimum' capacity, whereby the wave struction ofthe condenser We attain these various objects mainly CONDENSER.

1924. Serial No. 728,480.

by providing two sets of-movable plates which interleave, the movementof the plates being more nearly simply a gradual linear movement of oneset over the other. By arranging these plates so that they first overlapat the corners only, the desired uniformity of wave length is obtained.

Our invention possesses other advantageous features, some of which withthe foregoing, will be set forth at length in the following description,where we shall outline in full that form of the invention which we haveselected for illustration in the drawings accompanying and forming partof the present specification. Although we have shown in the drawings butone form of our invention, we do not desire to be limited thereto. sincethe invention as de scribed in the claims may be embodied in many otherforms also.

Referring to the drawings:

Figure 1 is a. top plan view of a condenser embodying our invention,shown as installed on a panel and in minimum capacity position; a

Fig. 2 is a rear view of the same, showing the plates in minimumcapacity position, and in alternate, maximum capacity position;

Fig. 3 is a sectional view, taken along plane 3-8 of Fig. 2; and

Fig. 4 is another sectional view, taken through the supporting rod forone of th sets of plates. 1

The two sets of plates may be conveniently designated as the left handset 11 and. the right hand set 12. In the present instance, there arefifteen plates in the left hand set, and sixteen in the right hand set,although the number may of course be varied to suit the requirements asregards capacity. These sets of plates are arranged to be manuallyrotated by a common mechanism, about axes provided by the rods 13 and14, which are stationary and, upon which are rotatably mounted thesleeves 15 and 16 respectively. Upon these sleeves are fastened, as bysoldering, the plates 11 and 12, which for this purpose are providedwith apertured ears 17 passing over the sleeve 15 or 16. These earsshown in dotted lines, where the sets of plates substantially completelyoverlap each other. It is to be noted that the overlapping of the platestarts at the upper adjacent corners 18, and that the overlappinggradually spreads from that corner as the sleeves and 16 are rotated.Due to this arrangement, the change in capacity withrelation.

to the amount of rotation of the plates,

- at first slow, when starting. from the minimum full linepositiombutincreases-substain tially unitormly-as that position departed fromSuch-aNarration, it, may no readily shown,-, is. essential in order tosecure-substa'ntial uniformity in the corresponding wavelengthyariationof the resonant circuit controlledby thecondenser.

Although allfiof the plates of each set are.

electricallyconnected through its respective sleeves 15 and 16,.weprefer to supplement the connection by the aid of the-smallturnedoverflaps 19 which1connect adjacent plates,

and whichiare stampeddntegrally withthem.

This furtherconnection alsovserves toistiifen the plates. Furthermore,these plates are shown as substantially rectangular, but withanarchedgtop; although to secure any desiredzcapacityvariation, thisform may aobviously be varied.

The mechanical construction whereby the movement: of the, plates issecured; will now bedescribed. The rods 13,14,- upon whichthe-sleeves-16 are rotatably mounted, are supported in any appropriatemanner, as for instance, on aflatinsulatingplate 20. In Fig. 1- thissupportis shown for rod 13,"but

the support for-rod l lais entirely similar.v

Rod 13 has a collar 21 either integral oriheld thereto in anyappropriateway, which collar engages one side of-plate 20. At-the otherside, vawasher-.22 is provided, and :a nut: 23-.engaging a threaded endof rod 13 serves to clamp the collar 21 firmly .21; ust the plate 20. Inorder to rotate slcere-1(' onrod 13, there is fastened to the sleere a.

collar 2%,to which in turii a gear wheelflt made of balzeliteor otherinsulating material, is held,.as by the aid of thepins 26; It is thusseen that by rotating wheel the plates 11 may be rotated about the ax ofrod 13. In order to prevent the sleeve 16 from-slippingoff the rod 13,and alsoto maintain'the plates 11 in proper frictional adjustment, a nut27 is used at the free end of rod 13 for engaging;theend of the sleeve.

The mechanical details for operatinglhc other set of "plates areentirely similar to that already described, the operating gear 28 forthe plates 12 being in mesh-With gear'25, whereby the rotation of onegear causes the 1 screws 36 pass;

rotation of the other also. In this why, both sets of plates are causedto rotate in opposite directions, so as to bring them either intointerleaving position or into the position shown in Fig. 2,

In order to lend rigidity to the structure, we preferably connect theends of the two rods 13, 1 1, by a strip 29 of insulating material." Ontop ofthis strip may be'placed the two terminals 30and 31 for thecondenser,

and the strip and terminals may be held securely to the rods 13, 14, bythe aid of nuts 32.. Theiconnections to the plates 11 and 12 may thus beprovided by these terminals, through rods-13 and- 1et,.and.sleeves .15,16'. However, we prefer" to provide a direct metal-l'ic connection fromtheterminals to theplates, without intervening; frictional. con.- tacts;For-- this purp osea-we .use the .p gtarl connections. .33 which aresoldered at one endto' a terminal, and .at its other endto thecollar3a26. The elimination'of the frictional contact ensures againstextraneous or parasitic-noiseswhen thecondenser is used in-aradiosystemn.

far described, it is evident that: the electric field,existinggbetween.the sets of As thus plates has but little. influence upon anydielectric material, because all. such material is at acomparativelylarge distance from this field. The main insulationsupports are the plate QOand'the strip 29,1Vl1lC-hfilllr' bracethe'plates, but do not; closely approach them Due to this-feature, thedielectric losses are-maintained-at a:.ve ry' low value. Furthermore thezleakageipaths between the electrodes are relatively. ,long," andvofsmall cross-sectional area; which minimizes loss due .to.surfaceleakagei Another important effect that may now be noted 1s thatin the 'minimumcapacity positionshown in Fig.2,

onlywthe cornersof .thesets of plates 11 and 12 areopposite'each other;there is therefore a-verylow minimum capacity, In other types ofcondensers, the sets ofplates in minimum-position, present acomparatively large area to each other.

The supporting :plate ported back of the panel a plurality of spacers 35through; which 20 is in turn -sup me-nt of the plates '11 and 12 about Itheir axes,- we provide a pair of stoppins on the insulation; gear 25,.which coact with a tened to a shaft 40 that is journaled. in a bushingt1 held-in the plateQO and extending-throughrthe panel-34;. The shaftoxtends for a considerable distance beyond the front of the panel, inorder to'makeit possible to fasten thereto an operating knob 42 In orderto limit the more-y lilll 34-, as by the aid of sired movementof theaccuracy in making fine, adjustments, vhich is soimp'ortant in tuningradio frequency circults. Furthermore, it is also to be noted that noelectrical .connections are made I 10 through the front of the panel.This fact reduces the effect of body capacity during timing.

In the present instance, the panel 34 is shown as fastened to a baseplate 44, but it is of course evident that other modes of supporting theentire structure may be used, if desired. Furthermore, in someinstances, a counterweight may be added to the sleeves 15 and 16 tobalance the rotating parts of the structure, and to ensure againstundeplates by the action of gravity. 3

The mode of operation of the condenser is it "believed to be evidentfrom the foregoing.

The knob 42 is simply turned in one or the other direction until thedesired setting is obtained.

Another advantage of the structure disclosed resides in the fact thatany number of condensers could begeared together so as to be operatedfrom a single knob, by merely mounting them at the proper spacing. Thusthe gear. 28 may be made to mesh directly with one of the operatinggears of a succeeding condenser.

We claim:

1. In a variable condenser, a pair of insulated electrodes havingcorners, and unitary means for simultaneously moving both electrodes insuch manner that they are caused to overlap to a variable extent to varythe I capacity thereof, the overlapping beginning at a corner of eachelectrode.

2. In a variable condenser, a pair of insulated electrodes havingcorners arranged to provide an electrical capacity by superposition, apair: of rotatable supports, one for each electrode, said supports beingso spaced. that by rotation thereof the electrodes maybe made to overlapto a variable extent, the overlapping beginning at a corner of eachelectrode, and unitary means for rotating both electrodes.

3. In a variable condenser for selectively 1 tuning an electricalcircuit, a pair of spaced shafts insulated from each other, a pair ofelectrodes insulated from each other and adapted to provide anelectrical capacity by superposition, one'electrode rotatably supportedon each shaft, and gears mechanically connecting the electrodes.

4. In a variable condenser for selectively tuning an electrical circuit,a pair of insulatedrotatable' electrodes arranged to provide anelectrical capacity by superposiapart, and a mechanical connectionbetween the electrodes, whereby both electrodes may be simultaneouslyrotated.

5. In a variable condenser for selectively tuning an electrical circuit,a pair of insulated spaced parallel rods, an insulating support for therods, a pair of electrodes arranged to provide an electrical capacity bysuperposition, one electrode rotatably mounted on each rod, and a gearfastened to each electrode and intermeshing, at leastone of said gearsbeing provided with insulation, and each of said gears being axiallyspaced from the corresponding electrode.

6. In a variable condenser, a pair of insu: lated spaced parallel rods,a pair of electrodes arranged to provide an electrical capacity bysuperposition, one electrode rotatably mounted on each rod, means forsimultaneously rotating the electrodes so as to vary the extent ofoverlap between them, means for holding the rods at one of their ends,terminals fastened to the rods at the other ends, and flexibleconnections between the terminals and the respective electrodes.

7. In a variable condenser, a pair of electrodes, each comprising aplurality of thin parallel plates, a rotatable sleeve for each electrodeto which the plates thereof are connected, a pair of spaced rods for thesleeves, gears of insulation material carried by the sleeves andintermeshing, an insulating plate on which each of the rods are fastenednear one of its ends, an insulating strip connecting the free ends ofthe rods, a terminal for each electrode in contact with that end of therod which is in connection with the strip, a flexible connection fromeach terminal to the corresponding rotatable sleeve, and a pinionengaging one of the gears.

8. In a variable condenser, a pair of insulated electrodes arranged toprovide an electrical capacity by overlapping, unitary means forsimultaneously moving both of the electrodes toward and from each otherto vary the capacity thereof, means movably supporting said. electrodes,a terminal for each electrode on said latter supporting means, and aflexible connection between the terminals and their respectiveelectrodes.

9. A variable condenser for selectively tuning an electrical circuitcomprising a base member, a pair of electrodes insulated from each otherand rotatably mounted upon said base, the respective axis of rotation ofthe electrodes being spaced laterally, and means including a singlemanually controlled shaft for simultaneously rotating said electrodes inopposite directionswhereby said electrodes are superposed a more or lessamount to vary the capacitance of the condenser.

10. A variable condenser comprising a base m mbene pa r o abl el ct espivotelly mounted upon said base member, said electrodes COlllLllSlIlgspaced plates adapted to interleave, the pivotal axis of the electrodesbeing spaced laterally, control means for simultaneously moving saidelectrodes, movement of each electrode through wlesa an arc oilessthan180 serving to vary the capacitancefrom a maximum to a minimum.

In testimony whereof, We have hereunto 10 t ur han ROGER M. WISE.

G. DANIELSON.

